If you visit most cities around the world, you're bound to see graffiti of some sort. San Francisco and Montreal are full of colorful murals, and you'll find similar art from Moscow to Buenos Aires. Reverse graffiti works a bit differently: much like the "wash me" notes that kids will swipe on the sides of dirty cars, artists create these images on soot- and dirt-covered surfaces by cleaning areas with scrapers and scrub brushes. The effects can be startlingly beautiful, as you can see in the images below:

The UK’s Paul Curtis, better known as “Moose,” is one of the technique’s pioneers. Although based in London, he has traveled around the world, creating images for clients such as Smirnoff. Commissioned by Süddeutsche Zeitung Magazin, Moose teamed up with Fotorater founder Marc Cameron to create images of eco-friendly cars like the Tesla Roadster around Munich. In addition to scrub brushes and scrapers, Moose often uses stencils and power hoses to etch fine detail into his work.

Brazilian eco-artist Alexandre Orion transformed a transport tunnel in Sao Paolo into a mural a few years ago by etching skulls into the exhaust-stained walls, and another Brazil-based street artist, Drin Cortes, creates incredible work on underpasses and walls around the country. It just goes to show that beauty can be created in the most unlikely places, and just about any material can be an art medium in the right hands.